The present invention relates to a bridge, and more particularly to a bridge which configures a spanning tree and is connected to neighbor bridges via plural paths. The present invention also relates to a method of improving the transmission efficiency of a bridge.
In order to avoid the looping of a packet in a conventional bridge, only one logical path is decided by setting ports of each bridge in a forwarding or blocking state by a spanning algorithm when plural paths configured by bridges exist within the same broadcast domain.
That is, when plural LANs (Local Area Networks) are interconnected in a loop state by bridges, broadcast packets are continuously relayed by each bridge without disappearance. However, when the number of packets to be relayed increase, the network is finally filled with them, thus resulting in a disabled state.
The spanning tree protocol compliant with the IEEE 802.1D standard is used to avoid such a condition. The spanning tree protocol is used to configure a tree configuration by logically separating off a looped communication line at a point.
Under the spanning tree protocol, bridges exchange a control packet being a BPDU (Bridge Protocol Data Unit) with each other. Thus a root bridge, being the apex of the spanning tree protocol, is decided based on ID, or identification information, inherent to a bridge. The root bridge periodically transmits a BPDU packet. When a bridge receives the BPDU packet, it transmits the same to a bridge which is downstream in the spanning tree.
As shown in FIG. 8(A), when there are plural paths between bridges 8 and 9, (e.g. two paths including one connected between ports 81 and 91 and the other connected between ports 82 and 92), only one path is selected by the spanning tree algorithm.
In this case, the bridge 8 controls the ports 81 and 82 while the bridge 9 controls the ports 91 and 92. Bridging is accomplished between the ports by creating the bridge table shown in FIG. 8(B) to handle as one logical port the two ports which physically exist. This allows packets to be freely transmitted to plural paths.
FIG. 8(B) shows a bridge table. A Mac address represents a Media Access Control address of the Data-Link Layer, or a terminal inherent address.
The conventional bridging technique has the disadvantage in that since only one path is selected among plural paths between bridges, any packet cannot be transmitted through the remaining paths.
The spanning tree specified by the IEEE standard, and so forth exists as means of preventing a broadcast stream from occurring because of the presence of plural paths between bridges. However, this algorithm restrictedly selects a single path when plural paths exist.
Moreover, the problem is that two bridges must provide the same function to use the paths therebetween.
The reason is that the general learning bridge causes the broadcast storm when only one bridge transmits packets via plural paths to transmit unknown Mac address or broadcast addresses to all ports.
The objective of the present invention is to solve the above-mentioned tasks.
Moreover, the objective of the invention is to provide a bridge capable of effectively utilizing plural paths connecting the bridge to neighbor bridges to communicate with the neighbor bridges, thus improving the transmission efficiency.
Furthermore, the objective of the present invention is to provide a method of improving the transmission efficiency of a bridge.
The objective of the present invention is achieved by a bridge which configures a spanning tree and is connected to neighbor bridges via plural paths, comprising a storage table for storing a pair of a transmission source address of a receive packet and a transmission destination port of the packet; a transmission destination decision registering means for deciding the transmission destination port by the transmission source address of the receive packet and then registering the transmission destination port on the storage table; and a transmission packet dividing means for transmitting packets from a specific port among ports corresponding to said plural paths when packets to be transmitted to the plural paths are broadcast packets or BPDU (Bridge Protocol Data Unit) packets of the spanning tree and for referring to the storage table when the packets to be transmitted to the plural paths are not broadcast packets or BPDU packets and then transmitting the packets to a corresponding transmission destination port.
In the bridge according to the present invention, the transmission source address on the storage table stores aging time information representing a registration elapse time; and the transmission source port on the storage table stores aging time information representing a registration elapse time; and the transmission packet dividing means resets corresponding aging time information upon referring to the storage table.
According to the present invention, the bridge further comprises received packet dividing means for receiving a BPDU packet and a broadcast packet and then transmitting them to the next stage, the BPDU packet and the broadcast packet being transmitted from the specific port among the ports respectively corresponding to the paths.
In the bridge according to the present invention, the received packet dividing means refers to the storage table according to the transmission destination address of the received packet from a port corresponding to each of the paths and then discards the received packet when the corresponding transmission destination port differs from a receive port.
In the bridge according to the present invention, the received packet dividing means refers to the storage table according to the transmission destination address of the received packet from a port corresponding to each of the paths and then discards the received packet when the corresponding transmission destination port is the same as a receive port and said transmission source address is registered on the storage table and information on the corresponding aging time registered on the storage table is smaller than a predetermined time.
In function, path division is decided for each Mac address of a transmission source to plural paths between the bridge according to the present invention and a general learning bridge. A port which transmits and receives a BPDU packet or broadcast packet in a spanning tree is selected as a specific port among plural paths. Thus, traffic can be distributed to plural paths while the spanning tree is being used.
Moreover, according to the present invention, a method of improving the efficiency of a bridge which configures a spanning tree and is connected to neighbor bridges via plural paths, comprises the steps of storing a pair of a transmission source address of a receive packet and a transmission destination port of the packet into a storage table; deciding the transmission destination port by the transmission source address of the receive packet and then registering the transmission destination port on the storage table; and transmitting packets from a specific port among ports corresponding to the plural paths when packets to be transmitted to the plural paths are broadcast packets or BPDU (Bridge Protocol Data Unit) packets of the spanning tree and for referring to the storage table when the packets to be transmitted to the plural paths are not broadcast packets or BPDU packets and then transmitting the packets to a corresponding transmission destination port.